Sony Ericsson has confirmed that owners of its Xperia X10 smartphone can expect an update to Android 2.1 ‘Eclair’ before the end of September — for customers in the United Kingdom, at least. Since the confirmation comes via tweet from the manufacturer’s UK Twitter account, it is unclear if other regions or countries will see the upgrade as well. The Snapdragon-powered X10 has been rumored to get a taste of Eclair since back in February, as the device comes with Android 1.6 out of the box.

At this point it may seem strange to push out a 2.1 upgrade when many other devices are already being updated with Android 2.2 ‘Froyo,’ however, customers should bear in mind that carriers aren’t simply releasing stock builds of the open-source operating system. Rather, they need to tailor their ROMs with carrier-specific applications that require weeks or months of testing and basically ensure a lag between upgrade plans and an actual release.

Recent US purchasers of the X10, which has gone on sale at AT&T in only the past few weeks, are fairly likely to see a version bump at some point as well, if only to address the performance issues about which some users have been quite vocal.